This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-342668, filed Nov. 26, 2002, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an ink-jet printing apparatus that can stabilize the image quality.
2. Description of the Related Art
Ink-jet printing apparatus adapted to prevent feathering and blurring among different colors from taking place are known (see, inter alia, Jpn. Pat. Appln. KOKAI Publication No. 8-216392).
With known printing apparatus comprising a plurality of discharge units, UV inks or solvent inks that are regulated so as to show a constant level of surface tension are discharged from the discharge units to form an image. Then, the discharged inks are fixed to the medium by means of a UV-setting device or a drier in a subsequent step.
With known printing apparatus, the inks discharged from the respective discharge units produce ink dots with different diameters, which are then fixed to the medium. However, a high quality image cannot be formed by ink dots having different diameters. Particularly, the time spent for the ink droplet discharged from the leading discharge unit to get to the fixing unit and the time spent for the ink droplet discharged from the tail end discharge unit to get to the fixing unit show the largest difference. This difference results in a remarkable difference of dot diameters and a poor image quality.
If the surface tension is differentiated among inks to dissolve the above problem, adjacently located inks can give rise to bleeding, which by turn produces a poor image quality. Therefore, there is a difficult problem of tradeoff.
An object of the present invention is to provide an ink-jet printing apparatus that can produce high quality images.
According to an aspect of the invention, there is provided an ink-jet printing apparatus comprising: at least two or more than two ink-jet heads provided with respective discharge ports for discharging ink and arranged in the direction of conveyance of recording medium; a conveyor for conveying a recording medium; and a drive section for driving the ink-jet heads so as to discharge inks toward the recording medium being conveyed by the conveyor;
the inks discharged form the respective ink-jet heads being made to show different surface tensions.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.